This invention relates to a whole house attic ventilating fan, and more particularly to such an attic ventilating fan and to a method of installing the fan in which the fan is installable from below in an opening cut in the ceiling sheathing of the house such that access to the attic crawl space is not required for installation of the fan when the fan is installed in a ceiling housing its joists on a common on-center spacing (e.g., 24 inches).
In general, whole house ventilating fans are utilized to draw cooler outside air into the living space of a house through open windows or doors, to force the air into the attic space of the house, and to exhaust air from the attic space to the outside via attic vents or the like. In the summer, such whole house ventilating fans result in cooler, outside air being circulated through the house such that the moving air feels significantly cooler to the occupants of the house. Further, by forcing outside air into the attic space and by thus displacing air from within the attic space to the outside via proper attic vents, the temperature of the air within the attic space can be significantly lowered on hot days. It will be appreciated that extreme air temperatures (e.g., 140.degree. F. or more) may be present in an attic which is not power ventilated. This heated air within the attic will heat the ceiling of the house, even though the ceiling may be well insulated. In well insulated houses, the highest temperature of the ceiling may not be attained for several hours past the heat of the day due to the thermal lag of the insulated ceiling. Thus, in the evening, when the ceiling reaches its highest temperature, the heated ceiling will radiantly heat the occupants of the house making it feel significantly warmer within the house than the ambient air temperature within the house.
Whole house ventilating fans have long been used to economically and efficiently circulate air through the living space of the house and to exhaust heated air from the attic space. Typically, whole house ventilating fans may be mounted vertically in an attic gable wall, in the roof, or horizontally in the ceiling of the house. The present invention is most particularly concerned with the horizontal mounting of whole house ventilating fans in an opening provided in the ceiling of the house with this opening in the ceiling providing communication between the living space of the house and the attic space. With such an installation, it is generally desirable to locate the fan centrally within the house so that air may be uniformly drawn from all parts of the living space of the house toward the fan, depending on which windows or doors of the house are open. For example, in a one story house, the fan may be located in a central hallway ceiling leading from the living areas of the house to the bedrooms.
In many prior whole house ceiling ventilating fans, it was necessary to first determine the best location for the fan and to cut a rectangular opening of predetermined size in the ceiling sheathing (e.g., the drywall) of the house. Since these whole house ventilating fans are usually of a relatively large size (e.g., the fan blades may have a diameter of 36 inches (91.4 cm.) or larger), the fan opening in the ceiling was, of necessity, relatively large such that one or more of the ceiling joists of the house would extend across the ceiling opening. Ceiling joists may, for example, be the bottom chords of prefabricated roof trusses. In many types of home construction, the ceiling sheathing is nailed to the bottom faces of the roof truss bottom chords or roof joists. These ceiling joists may be placed at uniform distances relative to one another, typically on 16 inch (40.6 cm.) or 24 inch (61 cm.) centers, and are usually of 2.times.4, 2.times.6, 2.times.8, or 2.times.10 lumber, depending on the size of the house and the design of the roof. These joists would be cut and header plates (i.e., lumber of the same dimensions as the joists) would be nailed in place transversely between the uncut joists and to the ends of the cut joists so that the inner sides of adjacent uncut joists and the header plates form a plenum box slightly above the level of the ceiling sheathing. The fan would then be mounted on top of the joists, and plenum box and a venturi would often be provided so as to at least partially enclose the fan blades thereby to enhance the operating efficiency of the fan.
As can be appreciated, it is a major carpentry task, sometimes too involved for the "do-it-yourself" installer, to cut the ceiling joists and to nail the header plates in place. Also, by cutting the joists, the strength of the roof or the ceiling of the house could be unduly weakened. It will be appreciated that the joists, since they oftentimes constitute the lower chords of the roof trusses, carry a significant load, often a tension load, when the roof is heavily stressed, such as during a windstorm or when it carries a significant snow load.
In an effort to eliminate the necessity of having to cut the joists and having to install headplates, a fan was commercially introduced, as disclosed in the coassigned U.S. Pat. No. 4,325,550, which included a frame mountable on the tops of adjacent ceiling joists. A venturi carried by the fan frame defined a venturi throat and skirts were provided which depended downwardly from the venturi so as to sealingly mate with the upper surfaces of the ceiling sheathing thereby to form a plenum box with the skirts having prescored slots or other means therein so as to accommodate (i.e., to fit over) the ceiling joists extending across the ceiling opening. While this fan greatly facilitated installation because it eliminated the necessity of having to cut the ceiling joists and to install header plates, it was necessary for the installer to have access to the attic crawl space from above for installation of the fan. It will be appreciated that in many applications, only a limited crawl space (sometimes 2 feet or less) is available between the tops of the ceiling joists and the roof of the house making access to the fan from above difficult. Thus, there has been a longstanding need for a whole house fan which can be readily installed from below within the attic of the house in register with an opening in the ceiling sheathing without the necessity of having access to the attic crawlspace.